1. Field of the Invention
This invention relates to an apparatus and methods for the three-dimensional screen printing of images onto pallet-supported articles, such as clothing or other fabric material.
2. The Prior Art
The printing of images onto articles, e.g. T-shirts and the like, is commonly accomplished using screen printing machines. Generally, these machines are provided with pallet support means for transporting a series of printing pallets to and from various printing stations located along the length of the machine. The articles also may be carried on a conveyor belt. A screen printing apparatus of this general configuration is disclosed, for example, in U.S. Pat. No. 3,795,189, the disclosure of which is hereby incorporated by reference. In operation, each article to receive a print image is placed on a pallet so that the surface to be printed upon is exposed to the printing mechanism. The pallets are then indexed along a continuous path to one or more individual print stations where an image is transferred to the article positioned beneath the printing head. Alternatively, the articles may remain on a stationary print table and the screen may be carried from article to article.
It is often desirable to print more than one layer of ink, or other print media, upon a single article. To prevent smearing, the previous layer usually must be allowed to dry before the next layer is applied. When a viscous printing medium is used, such as those used in producing a three-dimensional printing effect, the thick print layer takes much longer to dry, thus slowing production. Another problem associated with three-dimensional screen printing is that a thick print image produces a very uneven surface on the article. If a further printing step is required, this unevenness prevents the next print screen from contacting the article in a smooth and continuous fashion, resulting in a poor print image. Because of this difficulty, three-dimensional images are sometimes produced by hand, resulting in a slow, labor-intensive, and consequently expensive method of production.